The proper regulation of gene expression is necessary in order for normal growth and development to occur. The transcription process represents the first step in selecting which genetic information the cell will use. However, the selection of the proper genes to decode is only the beginning. Once RNA polymerase and its associated factors identify the correct genes, the transcription process must insure accurate and efficient elongation until the complete transcription unit has been decoded. That is, while the accurate selection of which genes the cell needs to transcribe begins transcriptional regulation, efficient elongation determines whether or not the genetic information is converted into a product useful to the cell. There are a large number of genes in human, and other eukaryotic, cells and their viruses which are specifically regulated at the level of elongation. For example, these include several protooncogenes, (c-myc, c-myb, c-fos), adenosine deaminase, a collection of stress response genes, and HIV-1 and HIV-2. Clearly understanding the mechanisms which control transcription elongation through these and other genes is fundamental to understanding normal development as well as such diseases as cancer and AIDS. In order to increase our knowledge of the controls over the transcript elongation process, a genetic and biochemical approach would be most powerful. This combination is most easily carried out in the budding yeast, Saccharomyces cerevisiae. There is extensive conservation in the protein components and biochemical processes of transcription among eukaryotes. Thus, much of what is learned by studies of this yeast will be immediately applicable to similar reactions in mammalian cells. This proposal will address several questions about factors which regulate the elongation reaction of RNA polymerase II. While transcript elongation factor TFIIS will be analyzed in detail, the experimental design will also insure the identification and characterization of new factors in addition to TFIIS that participate in elongation control. The Specific Aims include: (1) Identify and characterize functional substitute(s) for transcript elongation TFIIS; (2) Identify proteins which interact with TFIIS and determine their functional relevance; (3) Identify amino acid residues important for TFIIS function in S. cerevisiae; (4) Identify sites which block elongation by S. cerevisiae RNA polymerase II in vivo and in vitro.